Quantitative Correlation between Hierarchical Nanofiller Structure and Rheology of Polymer/Fumed Silica Nanocomposites

Abstract

Understanding the mechanical reinforcement of polymer nanocomposites (PNCs) filled with agglomerated nanofillers has attracted considerable attention in the past century, but a quantitative description of linear rheology over a wide range of time scales is still a challenge at present. In this study, the hierarchical nanofiller structure and its relationship to the rheology of fumed silica-filled poly(methyl methacrylate) nanocomposites are quantitatively investigated using transmission electron microscopy, smallangle X-ray scattering, and rheological measurements. It is suggested that the polymer entanglements dominate the short-time rheological behavior of nanocomposites, and the enhancement in the rubbery modulus is controlled by the interfacial adsorption-induced entanglements, which depend on the effective surface fractal dimension of nanofillers. At a longer time scale, the discrete agglomerates and the particle networks dominate the modulus enhancement. It was found that there is a power−law relationship between the particle network modulus and the inter-agglomerate mesh size with an exponent of −5, corresponding to a chemical dimension of 1 and rigid particle chains. A new two-phase model is suggested for the linear rheology of PNCs, including the contribution of interfacial entanglements, discrete agglomerates, and particle networks. The linear viscoelasticity of PNCs can be quantitatively described using properly determined structural parameters of particle agglomerates.

Preparation and properties of rice husk ash silica filled natural rubber

“…G' of NR compound without RHAS showed a nonlinear decrease with increasing strain, which could be related to the disentanglements of NR chains 51 . When the RHAS loading increased from 30 to 70 phr, the Payne effect became more pronounced, which is mainly attributed to the destruction‐reformation of fillers 52 . With the increase of RHAS loading, the effective volume of NR was reduced, and the segmental mobility of NR was restricted, the presence of high modulus RHAS particles led to the increases of G' at low strains 38 .…”

“…51 When the RHAS loading increased from 30 to 70 phr, the Payne effect became more pronounced, which is mainly attributed to the destruction-reformation of fillers. 52 With the increase of RHAS loading, the effective volume of NR was reduced, and the segmental mobility of NR was restricted, the presence of high modulus RHAS particles led to the increases of G' at low strains. 38 Especially when RHAS loading increased from 50 to 70 phr, G' 0 increased significantly.…”

“…The values of tan δ at 0 and 60 C increased with the increase of RHAS loading, which should be attributed to that RHAS agglomeration increased the destructionreformation of fillers and tan δ value of RHAS/NR composites. 52…”

The Quest for Contrast in Digital Images of Micro-/Nanostructured Polymer Blends before and after CO2Foaming: General Interest of Directional Diffusive Filtering for Edge Enhancement

“…There is vast literature on the occurrence of multiphase materials composed of several phases with smooth interphases or sharp interfaces. Phases, interphases, and interfaces are of crucial importance in several domains of polymer science including control of material properties, − polymerization efficiency, − or refined characterizations of materials. ,− …”

“…Smooth interphases and sharp interfaces are more or less difficult to reveal, characterize, and quantify, particularly at the nanometer scale. At this scale level, transmission electron microscopy (TEM) or scanning electron microscopy (SEM) are often used to observe and characterize multiphase materials. ,,,,− The correct characterization of the materials requires typically 1) the use of a suitable contrasting method or a contrasting aid, e.g., sputtering for SEM or staining for TEM, 2) imaging under proper conditions (temperature, pressure, electron flow), and 3) the establishment of robust methods or refined image treatments, − in other words, a good image analysis, leading to a representative quantification of the different phases.…”